Diagnosis and Treatment of Acute Post-Operative Infections Following Primary Total Knee Arthroplasty

Craig J. Della Valle, MD

Introduction

Infection is among the most feared complications following primary total knee arthroplasty (TKA). Diagnosis can be extremely difficult in the early post-operative period secondary to normal post-operative pain, edema and peri-incisional erythema that make the appearance of the wound and normal cues to diagnosis extremely difficult.

Treatment is equally difficult as there is a paucity of literature on the topic, and the reported rates of success are variable without a clear consensus on appropriate treatment.

Diagnosis of Infection in the Early Post-Operative Period

While the ESR and CRP have been found to be useful in the diagnosis of chronic periprosthetic joint infection, there is minimal data on their utility in the early post- operative period where one would expect they would be elevated and thus traditional cut- off values (30mm/hr for the ESR and 10-15mg/L for the CRP).

Similarly, while the synovial fluid WBC count has been shown to be useful for the diagnosis of chronic PJI in several studies, there is only recent literature on the utility of this test within the first few weeks where large amounts of blood would be expected to be around the hip joint and some inflammation would be expected.

It has been our concern that if the values commonly used for the diagnosis of chronic PJI were utilized (~1,100 to 3,000 WBC/uL) with a differential of 60- 80% PMN were utilized at this early time point, we would be over diagnosing infection and unnecessary procedures would be performed

Treatment of Infection in the Early Post-Operative Period

Not a lot of literature to look to for guidance; most series are small, all are retrospective and the endpoints are variable and success is not uniformly defined. Most common treatment is an irrigation and debridement with exchange of the modular bearing surface (if present). Many have recently questioned the value of this intervention.

Irrigation and Debridement

Perform a full synovectomy and bearing surface exchange if possible (allows for better exposure particularly posteriorly) followed by six weeks of IV antibiotics (although again little data to support this precise time period of treatment) followed by a variable course of oral antibiotics ranging from no oral antibiotic treatment to lifelong suppression. Most studies suggest a success rate of ~50%

Several studies have suggested that infections with resistant organisms (such as MRSA) do worse (harder to eradicate and harder to find an effective oral agent for longer term treatment)

Similarly studies suggest that infections with Staphylococcal organisms do worse

More recent studies show that results are poor regardless of the organism and timing of the debridement

One recent study also suggested that a failed debridement MAY compromise your ability to eradicate the infection later (patients treated with a 2-stage exchange had a higher failure yet if they had a prior I+D)

Should we perform multiple debridements? Antibiotic beads as interim adjunct?

One Stage Exchange: More recent interest in exploring this technique.

Experience from Europe has been encouraging but requires removal of well fixed often times cemented components (not technically easy) and requires a stem?

No data available on its utility in the early post-operative period

Two-Stage Exchange: A “conservative” option?

No data on this option in the early postoperative period.

Not easy to remove components as above. Necessary? Timing between stages?

Bottom Line: I+D is still what I do as my first option, however...

Patients are counseled that the chance of success is 50% at best

Low threshold to proceed to a 2-Stage exchange if therapy appears to be failing

Clearly an area where further research is required to determine optimal treatment